• Question: Will Pluto ever be classed as a planet anymore? thx from u11wetherallp and u11gibsone

    Asked by to Becky, Clara, Daniel, Simon, Thomas on 13 Mar 2014. This question was also asked by .
    • Photo: Thomas Elias Cocolios

      Thomas Elias Cocolios answered on 13 Mar 2014:

      Not being an astronomer, this answer is only my personal opinion. What really matters is the definition of what a planet is, and I believe it is that its orbit is closed and that it is therefore bound to its star.

      Pluto does not fall in that category. It is however named a planetoid, which means that as far as its constitution, size, etc. is concerned, it is the same as a planet. It is simply not a bound member of the Solar System family, but rather a close relative that you see on special occasions!

    • Photo: Clara Nellist

      Clara Nellist answered on 13 Mar 2014:

      Sorry, I have to disagree a bit with Thomas on this question. Pluto does have a closed orbit (as far as I understand his definition of closed, meaning that it goes back to the same place), but the difference between pluto and the other planets is that it’s orbit is more egg shaped than circular. Which means sometimes it’s closer to the sun than Neptune and sometimes it’s further away. Pluto’s orbit is also tilted a lot compared to the others. In size, it’s pretty small compared to the other planets and has a moon almost the same size as it! Also, since it was discovered and named a planet, there have been other ‘rocks’ found that are of a similar size, such as Eris which is actually bigger than Pluto.

      It was decided then that either these new rocks were also called planets (and then we’d have 10 or 20 or more to learn the names of!) or that pluto would have to be down-graded to a dwarf-planet. It’s unlikely now that they’d class it as a planet again in the future.

    • Photo: Simon Albright

      Simon Albright answered on 14 Mar 2014:

      No, until recently there was no definiton of what a planet was so a group of astrophycisists got together to try and decide what makes a planet. They decided that to be a planet something must:

      1: orbit the sun (which Pluto does)
      2: be heavy enough to make istelf roughly spherical (which Pluto does)
      3: have cleared it’s local area (which Pluto hasn’t)

      Because there are other things orbiting on a similar path to Pluto it cannot be classes as a planet. And that actually makes more sense, there are other bodies similar sized, and some bigger than, Pluto but they were never classes as planets because of when we found them.

Comments